Dementia describes a set of symptoms that can include memory loss and difficulties thinking, and it is one of the UK’s leading killers.

The exact cause of the condition is unknown, but there are factors known to increase your risk - and breathing in toxic air could now be one of them.

MPs today warned that toxic air in Britain could potentially cause dementia, as well as increase likelihood of diabetes.

The shocking suggestions were made at a re-launched inquiry into improving air quality across the UK.

Dr Sarah Wollaston MP, chair of the health committee, said: “There is an increasing amount of evidence showing the impact of nitrogen dioxide and invisible particulates on human health.

“Many people are aware of their impact on our lungs and hearts, but new evidence suggests that they could also contribute to diseases as disparate as dementia and diabetes.”

There is a growing body of evidence suggesting that air pollution can harm the brain.

It is thought it could accelerate cognitive ageing, therefore increasing risk of Alzheimer’s disease and other types of dementia.

According to research published in January by the University of Southern California, air pollution could account for 21 per cent of dementia cases worldwide.

What’s more a study by the University of Toronto in the same month showed that people living within 50m of a major road were 12 per cent more likely to develop dementia than people living 200m away.

They found levels of fine pollutants were ten times higher within 50m of a major road compared to being 150m away.

These pollutants - also called particulate matter - are a mixture of extremely small particles and liquid droplets that get into the air.

Inhaling particulate matter is also known to affect the heart and lungs.

According to Friends of the Earth, the most polluted parts of the UK are Lambeth in London, Hammersmith and Fulham in London, Camden in London and Brighton and Hove.

The present inquiry - in which the dementia risk were discussed - was launched after the High Court decided that the Government’s plans to cut nitrogen dioxide air pollution were not sufficient enough.

It was initially postponed by the general election earlier this year, and was relaunched today.

Currently the Government’s plans include clean air zones’ and an end to the sale of petrol and diesel vehicles by 2040.